Catechins are reported to have physiological effects, such as an inhibitory action on α-amylase-activity (Patent Document 1). In order for such effects to materialize, a large amount of catechins must be consumed as easily as possible. Therefore, a technique that makes it possible for a food and drink to contain a high concentration of catechins has been sought.
As one of such conventional techniques, there is a method in which catechins are added to a food and drink (e.g., a beverage) by making use of a tea extract such as a concentrate of green tea extract. However, such a method is known to cause great damage to the commercial value of a food and beverage due to the residual bitterness and astringency stemming from caffeine and green tea, depending on its kind of food and beverage, for example, in the case where catechins are added to a black tea extract or a carbonated beverage.
Adsorption methods (Patent Documents 2 to 4) and extraction methods (Patent Documents 5 to 6) are known as effective for removing impurities (e.g., caffeine) from a tea extract. There are also techniques that have been recently disclosed, which includes improving taste by reducing flavonoids and flavonol aglycons inherently contained in a green tea extract. Examples thereof include a method for reducing the intensity of bitterness of a green tea extract, which contains epigallocatechin gallate and gallocatechin gallate, and providing it with an improved taste by controlling the percentage of gallate body in non-polymer catechins to 50 wt % or higher and flavonoids to 0.0025 or smaller to the sum of the epigallocatechin gallate and gallocatechin gallate (Patent Document 7); and a method for reducing unpleasant bitterness and astringency by controlling the percentage of gallate body in non-polymer catechins to 50 wt % or higher and flavonol aglycons to smaller than 0.002 to the non-polymer catechins (Patent Document 8). However, none of such convention methods have so far succeeded in improving the aftertaste subsequent to an intake, albeit having succeeded in improving bitterness.    [Patent Document 1] JP-A-03-133928    [Patent Document 2] JP-A-05-153910    [Patent Document 3] JP-A-08-109178    [Patent Document 4] JP-A-2002-335911    [Patent Document 5] JP-A-01-289447    [Patent Document 6] JP-A-59-219384    [Patent Document 7] JP-A-2006-129757    [Patent Document 8] JP-A-2007-001893